# std::filesystem::path::compare

From cppreference.com
< cpp‎ | filesystem‎ | path

int compare( const path& p ) const noexcept; | (1) | (since C++17)
int compare( const string_type& str ) const; int compare( std::basic_string_view<value_type> str ) const; | (2) | (since C++17)
int compare( const value_type* s ) const; | (3) | (since C++17)

Compares the lexical representations of the path and another path.

1) If root_name().native().compare(p.root_name().native()) is nonzero, returns that value.
Otherwise, if has_root_directory() != p.has_root_directory(), returns a value less than zero if `has_root_directory()` is false and a value greater than zero otherwise.
Otherwise returns a value less than, equal to or greater than ​0​ if the relative portion of the path (`relative_path()`) is respectively lexicographically less than, equal to or greater than the relative portion of p (p.relative_path()). Comparison is performed element-wise, as if by iterating both paths from `begin()` to `end()` and comparing the result of `native()` for each element.
2) Equivalent to compare(path(str)).
3) Equivalent to compare(path(s)).

### Parameters

p | - | a path to compare to
str | - | a string or string view representing path to compare to
s | - | a null-terminated string representing path to compare to

### Return value

A value less than ​0​ if the path is lexicographically less than the given path.

A value equal to ​0​ if the path is lexicographically equal to the given path.

A value greater than ​0​ if the path is lexicographically greater than the given path.

### Exceptions

2,3) May throw implementation-defined exceptions.

### Notes

For two-way comparisons, binary operators may be more suitable.

### Example

Run this code

    #include <filesystem>
    #include <iostream>
    #include <string_view>
    namespace fs = std::filesystem;

    void demo(fs::path p1, fs::path p2, std::string_view msg)
    {
        std::cout << p1;
        const int rc = p1.compare(p2);
        if (rc < 0)
            std::cout << " < ";
        else if (rc > 0)
            std::cout << " > ";
        else
            std::cout << " == ";
        std::cout << p2 << " \t: " << msg << '\n';
    }

    int main()
    {
        demo("/a/b/", "/a/b/", "simple");
        demo("/a/b/", "/a/b/c", "simple");
        demo("/a/b/../b", "/a/b", "no canonical conversion");
        demo("/a/b", "/a/b/.", "no canonical conversion");
        demo("/a/b/", "a/c", "absolute paths order after relative ones");
    }

Output:

    "/a/b/" == "/a/b/"      : simple
    "/a/b/" < "/a/b/c"	: simple
    "/a/b/../b" > "/a/b"	: no canonical conversion
    "/a/b" < "/a/b/."	: no canonical conversion
    "/a/b/" > "a/c"	        : absolute paths order after relative ones

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 2936 | C++17 | compared all path elements directly | root name and root directory handled separately

### See also

operator==operator!=operator<operator<=operator>operator>=operator<=> (C++17)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++17)(until C++20)(C++20) | lexicographically compares two paths (function)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/filesystem/path/compare&oldid=158016"